General Comments on Tolerancing Limits

This represents a general list of soft limits and is intended for reference only.

Reducing tolerance range increases costs.

Robust sensitivity analyses will help yield the most cost-effective tolerancing.

Tolerancing Limits for Cylinder Surfaces

wdt_IDAttributeCylinder Tolerancing Limit
1Glass Quality (nd, vd)Melt Rebalanced and Controlled
2Length and width (mm)+0, -0.020
3Center Thickness (mm)³± 0.020 
4Sag – Concave (mm) ± 0.020 
5Clear Aperture 100%⁴
6Radius⁵± 0.1% or 3 HeNe fringes⁶
7Irregularity – Interferometry (HeNe fringes)⁷0.1⁸
8Irregularity – Profilometry (μm) ± 0.5 
9Plano Axis Wedge – ETD (mm) 0.005¹²
10Cylinder Axis Decentration – TIR (mm)⁹0.010¹⁰
11Axial Twist Angle (arcminutes) 
12Bevels – Face Width @ 45° (mm)¹¹0/0mm max
13Scratch – Dig (MIL-PRF-13830B)¹²10 – 5 
14Surface Roughness (Å RMS)¹³
  1. This is for the most well behaved materials. More difficult materials (CaF2, Ohara S-FPL, etc.) will need larger tolerance ranges.
  2. Of full aperture (FA).
  3. In addition to irregularity.
  4. Whichever is correspondingly larger over the clear aperture.
  5. Typical metrology is Zygo MetroPro plots for interferometry.
  6. As geometry requirements move closer to a min or max shown the less likely this is possible.
  7. Optimax measures total indicated runout (TIR) as part is rotated. Actual decentration varies with focal length.
  8. This specification is extremely tight and expensive. For a more economical limit, please consider using 0.0100mm.
  9. Subject to measurement uncertainty.
  10. Crystals and reflective materials will receive 40W inspection.
  11. This represents lowest values obtained. Actual values for crystalline, especially polycrystalline materials, will be higher.

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